The invention relates to an improved latching apparatus for closing and opening a cover door used for closing an access opening in a bulk storage structure such as a grain bin wherein the structure and cover door will be exposed to significant forces exerted thereon by the weight of the material being stored therein.
In order to improve the structural integrity of such a bulk storage structure, it has been suggested in U.S. Pat. No. 4,913,478, the disclosure of which is incorporated herein by reference thereto, that the cover member be supplied with a plurality of bores which engage with respective protuberances or pins on the storage structure adjacent the access opening. Thus, as hoop stresses are applied to the storage structure by the weight of the material being stored, the hoop stresses can pass through the cover member by means of the tensile force exerted between a structure protuberance and a respective cover member bore.
It has been discovered, however, that when the aforementioned hoop stresses are applied to the storage structure with an engaged or integrated cover member, slight deformations occur in the structures which cause the cover bores to bind or stick on the protuberances thereby causing great difficulty in disengaging the protuberances from the bores and preventing facile opening of the cover member. In some cases it has been necessary to use a sledge hammer or the like to ram the cover member open. This procedure, of course, may cause permanent damage to the cover member or the adjacent jamb requiring expensive replacement or repair, and cause the entire storage structure to be unusable for a significant period of time.